The smartphone world is relatively new, so I suspect there are amazing (yet sometimes unknown) apps that can help various aspects of our lives. I cannot think of a better discussion place for this topic. So,

Which app help you optimize life?

Is there an app you keep searching for in vain? (though it might exist!)

For me (I was searching for both apps for months!! until they were finally created):

Anki, A flashcard memorization app with many useful features.

[From the link] Anki is a program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.
Anyone who needs to remember things in their daily life can benefit from Anki. Since it is content-agnostic and supports images, audio, videos and scientific markup (via LaTeX), the possibilities are endless.

Simple Counter Widget, A counter widget. Sounds simple, but it's amazingly helpful.
I use it as a tool to better myself. Every time I eat my gum (an annoying mostly unconscious habit), the gum-eating-widget is increased by one. Because the widget is so accessible, I rarely cheat. This gives the habit immediate negative feedback, and allows me to check improvement over time. (Also my desktop looks cool, with many intriguing numbers popping from everywhere)

(less interesting: Record Mic and Call - which includes a useful recording widget, and Waze - which is amazing but well known GPS app (at least here))

please share to make this interesting :)